What is the primary effect of diffraction in optics?

The primary effect of diffraction in optics is the bending of light around obstacles. This phenomenon occurs when a wave encounters an edge or an aperture that is comparable in size to its wavelength. As light waves pass around the edges of an obstacle or through a narrow opening, they spread out rather than simply continuing in a straight line. This bending and spreading effect can lead to patterns of light and dark regions, known as interference patterns, as the waves overlap.

In diffraction, the degree of bending depends on the relationship between the wavelength of the light and the size of the obstacle or opening. When the size of the obstacle or aperture is similar to the wavelength, significant diffraction occurs, resulting in a noticeable spreading of the light waves. This characteristic behavior of light is fundamental to various optical phenomena, including the patterns observed in experiments like the single-slit diffraction experiment.

The other choices relate to different optical phenomena and do not accurately describe diffraction. Light paths that travel straight without deviation are not influenced by diffraction. The change in color of light as it passes through a prism refers to dispersion, while the splitting of light into two parallel beams does not align with the concept of diffraction, as it suggests a different mechanism, such as refraction or the action of beam splitters.